The "Blue" Bottle Demo

• gloves
• goggles
• lab coat
• 250 mL erlinmeyer flask with rubber stopper (or bottle of equivalent size)
• 100 mL of a 5% NaOH solution
• 5 grams of glucose
• 1-2 mL of a 0.1% solution of indigo carmine in water
• plastic pipet or eye dropper

1. Pour sodium hydroxide solution into flask.
2. Add 5 grams of glucose and allow to dissolve.
3. Add the deep blue indigo carmine solution. Solution should immediately turn yellow-green.
4. Carefully stopper the flask.
5. Shake to mix solution and ensure yellow-green color.
6. Set the flask aside (this is a good time to explain the chemistry of the demonstration). The liquid will gradually become red as glucose is oxidized by the dissolved oxygen. A thin yellow boundary can be expected to remain at the solution-air interface, since oxygen remains available via diffusion.
7. The yellow-green color of the solution can be restored by swirling or shaking the contents of the flask.
8. The reaction can be repeated many times.

• Be careful with the hydroxide solution, it is corrosive.
• The reaction can be performed with methylene blue to make a solution that alternates between colorless and blue. Indigo carmine is more colorful and almost non-toxic.
• The warmer the solution is the more green (rather than yellow) it will be after shaking.
• The reaction neutralizes over time and can be safely poured down the sink after the demo.

Here is a video of the traditional blue bottle experiment using methylene blue: